What does the Speed Timing Sensor do? The sensor is a magnetic coil mounted on the engine block that measures the rotation of a componen? which tells the engine control module to determine how the engine settings should be adjusted . How do you know you need your Speed Timing Sensor needs to be replaced? Low coolant light is on Lack of power Check Engine light is on How are the Speed Timing Sensors replaced by a mobile mechanic? Remove the engine trim cover. Remove the defective speed timing sensor. Install the new speed timing sensor. Reinstall the engine trim cover. Take the vehicle on a road test and speed timing sensor operation is checked. How important is having your speed timing sensor repaired? If the speed timing sensor is not working properly the engine performance is reduced and will not run properly .